Inductance coil



w. A. MARRlsoN' 1,836,808

INDUCTANE coIL Dec. 15, 1931.

-Pgamdnwislssi UNITED STATES PATENT OFFICE Wm L mmol', 0l' mi), m m, AISIGIOB wm m0 mum, IINBPQBATID, 0l' m YORK, Il. Y., A. CORPORATION 0l' m mirarnos corr.

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This invention relates to inductance coils suoliasareusedinelectricalcircuits.v

It is well known that inductance coils Y change their inductance with changes in temperature. These variations are likely to pre lventthebesto f chtion of the cinrgxit for the purpose orw' itisesi anare therefore objectionable.

The object of this invention is to produce m 'an inductance coil having azero temperature ,with respect to others. u In one embodiment of 'coecient The inductance of a coil depends upon a number of factors, among them its cross-sectional area, and length, and its physical reu' lationto other`coils in inductive relation to it. Due to the ex ansion and contraction of the conductor which forms the coil, and of the form -on which the coil is wound, these factors tend to vary with variations in temperature. The constancy of inductance of a coil with temperature chan therefore is a function of the constancy o these factors or of a compensating variation of some of them y l this invention materials having zero tem erature coeicients of expansionl are used, or example, copper plated invar is wound on a quartz form.

As an alternative to this', phos hor bronze 30 wire under tension may be woun on a rigid quartz form. Due to the elasticity of the wire the coil will not change dimensions, but

will retain the dimensions of the quartz form.

In Ianother embodiment means are provided for maintaining the cross sectional area of a coil substantially constant despite the exv pansion or contraction of thewindings or frame. g

- If two coils are wound in series and so placed that their fields overlap, the inductance ofthe coils will vary with variations in their mutual inductance. If two coils so wound' and placed are subjected to temperature changes, their inductance will vary principally withchanges in the area and length of the coils,'and wlth changes in their mutual inductance due to change in area. These variations may be controlled to give the coils a temperature coeicient in a desired sense, and compensated by providing means for chang# ing the relative 'tion f the coils and hence tance as needed.

In a third embodiment two such coils 'are mounted on a base havingla temperature coeicient of expansion suc that the relative sition of the coils is varied, with variations 1n temperature, and their inductance remains constant. The coils may be co-axial or not, as desired.

In the drawings Figs. 1 and 2 show inductance coils having constant area and Figs. 3 and 4 show inductance coils of variable area, whose inductance changes with changes in area are compensated.

In Fig. 1, two end pieces 1, 2, of bakelite or other suitable insulating material, with shoulders of dierent diameter to engage col-A lars associated therewith, are fastened together by means of a screw-headed bolt 3 secured by a nut 4. Engaged by said end pieces 1, 2 is a collar 5 of suitable insulating material, on which is wound a plurality of turns of wire 6, to serve as a cou ling coil for the coil to be hereafter descri d. Between said end pieces 1, 2 and engaged thereby is a second collar 7 of quartz, or other suitable insulating material having a very low or' zero temperature coeicient of expansion. Wound on said collar 7 is a winding 8 consisting of a plurality of turns of wire made of invar steel, or other suitable material having a very low or zero temperature coecient of expansion. Copper plated invar is a desirable alternative to invar as a zero temperature coecient material. As the temperature of the form 7 or of winding 8 changes there will be no change in the dimensions of these Y solution and then dipping each end into this solution again.

Instead of using invar steel for the winding 8 in this figure, wire made of phosphor bronze wound under tension may be used.

-Due to the elasticity of this wire it will follow the quartz form instead of changing dimensions with changes in temperature.

In Fig. 2 a base 9 supports four corner posts 10, 11, 12, 13 around which is wound a winding 14 consisting of a plurality of turns of an electrical conducter whose ends are secured to binding posts 15, 16. Mid-way between the corner posts are four movable re# 15 straining members 17, 18, 19, 20. Connected to opposite restraining members are springs 21, 22. When the temperature rises, causing the base 9 to expand tending to increase the area of the coil and causing the corner posts to lengthen, tending to increase the length of the coil, the electrical conductor also lengthens. As the ends of the coil are fixed this creates a slack which is taken up by the springs attached to the restraining members and the sides of the coil are drawn inward, maintaining the area constant, or decreasing 'it to compensate the change in length, and' thus tending to decrease the inductance of the coil, and compensating for the changes tending to increase its inductance. Y

In Fig. 3 a base 30 has two shelves 31, 32 extending from its ends, over said base. These shelves may be an integral part of the base or may be separate members ixedly secured thereto. Mounted on said shelves are two coils 33, 34 consisting of a plurality of turns of an electrical conductor' wound in series. As the temperature increases the area ofthe coils 33, 34' increases, tending to increase the inductance of the coils. However, the base will lengthen, tending to separate the coils, while. the shelves 31, 32 will also lengthen tending to bring the coils closer together. The base being made 'of material havin a dii'erent temperature coeiiicient than t e shelves in one case, or if made of the same material, being of greater length, it ex erts the major effect in determining the relative position of the coils so that the dis- 5 tance between them increases and the tendency of the coils to increase in inductance due. to increase in area is compensated by this separation. The shelves may be made of different materials to effect a dierential compensation, if desired.

In Fig. 4 the parts of a divided coil 40, 41 are wound in series on forms 42, 43, and coaxially secured to opposite ends of a central supporting member 45. Form 42 is secured to member 45 by a tight it and form 43 by means of screw 47. The supporting member is secured to a base 44 by vmeans of the screw 46. As the temperature increases, the area of the windings 40, 41 increases, tending to increase the inductance of the coil. This is compensated, however, by the increased distance between the coils caused by the expansion of the supporting member 45.

The compensating e'ects described above may not be the same over a large temperature range due to the different coeflicients of expansion of the materials chosen at different temperatures, but the materials may be so chosen thatthe minimum deviation in inductance occurs at a desired temperature, so that over a considerable range in this neighborhood, the deviation of inductance from a constant value will be effectively zero.

What is claimed is:

1. A coil comprising a plurality of turns S0 of an electrical conductor, having a zero temperature coefficient of inductance.

2. An inductance device comprising a plurality of inductance coils mounted on a base or mounting adapted to vary the distance between said coils 1to compensate their increase in varea with temperature variations, to maintain the inductance constant.

3. An inductance element comprising a plurality of coils wound in series and a plurality of mounting members to which said coils are secured, whereby the inductance of said element remains constant irrespective of temperature variations.

4. In combination, a plurality of coaxially V related coils connected in series, and means for changing the separation between said coils `'with temperature changes.

5. An inductance element comprising la. plurality of coils electrically connected to- .10 gether, said element having a zero temperature coeiicient ofinductance.

6. In combination, an inductance element comprising a plurality of coils, and means for compensating variations in the inductanceof said element due to temperature changes.

7. In combination, an inductance element comprising a plurality of coils electrically connected, and mounting means for producing a change in the spacing arrangement of said coils.

8. An inductance coil, comprising a lplurality of turns of an electrical conductor aving a zero temperature coeliicient of expansion, wound on a form having a zero temperature 11 coeicient of expansion.

9. An inductance coil, comprising a'- plurality of turns of an electrical conductor made of copper plated invar, wound on a frame made of quartz.

10. An inductance coil, comprising a plurality of turns of elastic wire wound on a frame having a coeliicient of expansion equal approximately to zero. s Y.

11. An inductance coil, comprisingxa plurality of turns of an electrical conductor adapted to have a constant cross-sectional area irrespective of variations in tempera-l ture. v

12. An inductance coil comprising a quartz form and a plurality of turns of elastic bronze wire wound thereon.

13. An inductance coil comprising a base, a plurality of supporting members supported on said base, a plurality of turns of an electrical conductor wound on said supporting members, a plurality of movable restraining members associated with said coil, and springs connected to oppositely disposed restraining members.

In Witness whereof, I hereunto subscribe my name this th day of July, 1929.

' WARREN. A. MARRISON. 

